The invention relates to an air treatment system for supplying a commercial vehicle brake system with compressed air. The system includes a compressed air outlet which is provided for supplying a parking brake system and which is intended for ventilating at least one spring-loaded cylinder of a parking brake, and thus consequently for releasing the parking brake.
The invention relates, furthermore, to a method for ventilating at least one spring-loaded cylinder of a parking brake and thus for releasing the parking brake of a commercial vehicle brake system which is supplied with compressed air by an air treatment system. The air treatment system has a compressed air outlet provided for supplying the parking brake system.
Generic air treatment systems fulfill numerous functions regarding the supply of compressed air to a commercial vehicle. The air treatment systems serve, inter alia, for supplying the brake system of a commercial vehicle with compressed air. In particular, compressed air reservoirs are filled with air via air treatment systems, in order thereby to make a stock or supply of compressed air available for the various brake circuits. In a commercial vehicle with two brake circuits for the service brake system, it is necessary to provide a compressed air reservoir for each of these brake circuits. In general, there is a third compressed air reservoir, which provides a stock of compressed air for the trailer brake system (“circuit 3”).
The parking brake system of commercial vehicles also operates with compressed air. In order for the vehicle to be kept stationary, with the engine switched off and therefore with the compressor switched off, spring-loaded cylinders are provided in the parking brake system, which make the required parking brake action available by means of a spring force. To release the parking brakes, the spring-loaded cylinders are ventilated, so that the spring force is counteracted, with the result that the parking brakes can be released. In order to induce such a release of the parking brake system, it is therefore necessary for compressed air to be present at the respective outlet of the air treatment system, and, furthermore, that a handbrake valve, which is generally provided between the spring-loaded cylinders and the compressed air outlet, is brought into the release position.
The operation of a vehicle with a parking brake system of this type presents no problems when the handbrake valve is released at a pressure which is sufficient to release the parking brake. If, however, there is no pressure or only a low pressure present at the compressed air outlet for the parking brake system, then the opening of the handbrake valve may initially not bring about a release of the parking brake system. If a sufficient pressure for releasing the parking brake system is then built up later, this release takes place at a time interval uncorrelated with the opening of the handbrake valve. This entails risks. If, for example, the driver warms up the engine on cold winter days, opens the handbrake valve and then leaves the vehicle in order to remove ice from the vehicle windows, then compressed air is in time built up. When there is sufficient compressed air, therefore, the spring-loaded cylinders are ventilated, and an unintentional and unexpected release of the parking brake system occurs. The vehicle may thus be inadvertently set in motion.
The object on which the invention is based is to overcome the problems of the prior art and, in particular, to avoid the risk of unintentional release of the parking brake system.
The invention builds on the generic air treatment system in that an electrically actuable valve is provided, by which a supply of the compressed air to the compressed air outlet can be prevented, in that, when a person for driving the commercial vehicle is present, an electrically evaluatable indicator can be made available, and in that the electrically actuable valve prevents the supply of the compressed air outlet with compressed air when the indicator is absent. This ensures that an unintentional ventilation of the spring-loaded cylinders of the parking brake system cannot occur. Instead, a ventilation of the spring-loaded cylinders can take place only when a person for driving the commercial vehicle is present and, consequently, an electrically evaluatable indicator is made available. If this indicator is absent, an electrically actuable valve is induced to shut off the supply of compressed air to the compressed air outlet of the parking brake system. Furthermore, the lack of a third reservoir ensures that an unintentional ventilation of the spring-loaded cylinders is also avoided in this way.
Beneficially, there is provision for the compressed air outlet to be supplied with compressed air via an overflow valve and for the electrically actuable valve to be a solenoid valve which shuts off the overflow valve in at least one switching state. The solenoid valve can be activated in a simple way and as a function of the presence of an electrically evaluatable indicator. The overflow valve can be shut off, depending on the switching state of the solenoid valve.
The invention is developed especially advantageously in that the solenoid valve is a 3/2-way valve which, in a first switching state, ventilates a control inlet of the overflow valve and, in a second switching state, acts with pressure upon the control inlet of the overflow valve, with the result that the overflow valve is shut off. The compressed air supply is connected to one connection of the solenoid valve, and the control inlet of the overflow valve is connected to another connection of the solenoid valve. Furthermore, an outlet is available for ventilation. Thus, in one switching state of the 3/2-way valve in which the compressed air inlet is connected to the compressed air outlet, with compressed air present at the inlet the control inlet of the overflow valve is acted upon by pressure. In the other switching state, that connection of the 3/2-way valve which is connected to the control inlet of the overflow valve is connected to the ventilating outlet, so that the control inlet can thereby be ventilated. In addition to the direct activation of the overflow valve by the solenoid valve preferably being designed as a 3/2-way valve, it is also contemplated to use a solenoid valve for the pneumatic activation of a pilot control valve and, thereby, to implement the respective switching states.
It is preferable that the second switching state of the 3/2-way solenoid valve is brought about by the application of current to the 3/2-way solenoid valve. Since it is only ever necessary to shut off the overflow valve for a short time during the build-up of compressed air in the compressed air system of the commercial vehicle, the switching logics addressed ensure as short a current application time of the solenoid valve as possible.
In one embodiment, there may be provision for the solenoid valve to be supplied centrally with compressed air. In this case, the overflow valve can be shut off whenever the compressor delivers pressure.
It may also be beneficial, however, that the solenoid valve is supplied with compressed air by at least one service brake circuit. In this case, the reservoirs of the service brake system can make the required control pressure available for the overflow valve.
In the air treatment system according to the invention, there is beneficially provision for the compressed air outlet to be connected to the at least one spring-loaded cylinder via a handbrake valve. There are, therefore, at least two necessary conditions for the ventilation of a spring-loaded cylinder, to be precise, first, an open handbrake valve and, second, an overflow valve which is not shut off.
It is preferable that the electrically evaluatable indicator is made available as a result of the actuation of a pedal in the driver's cab of the commercial vehicle. The tapping of the accelerator pedal, of the brake pedal, or of the clutch pedal may be considered as an example of this. This involves the generation of reliable indicators, since such tapping of the pedal assembly is possible only when a person is present in the driver's cab of the commercial vehicle.
It may likewise be expedient that the electrically evaluatable indicator is made available as a result of the fastening of a safety belt in the driver's cab of the commercial vehicle. A fastened safety belt, too, is generally a reliable criterion for the presence of a person.
The air treatment system according to the invention is advantageously developed in that the electrically evaluatable indicator can be supplied directly or indirectly to an electrical control via a data bus, and in that the electrically actuable valve can be actuated by the electrical control. The electrical signal generated, for example, by the tapping of a pedal can be made available, for example, to a vehicle management computer, which then transfers an electrical signal transmission to the electrical control of the air treatment system via a central plug. The solenoid valve directly activatable by the air treatment system may then be activated as a function of the presence of the indicator.
Furthermore, there is advantageously provision for a signal device to be provided in the driver's cab of the commercial vehicle. The signal device indicates that a minimum pressure for operating the service brake system is overshot, and for the compressed air outlet to be supplied with compressed air in the event of the overshooting of the minimum pressure and with the indicator present. As soon as there is sufficient pressure in the service brake system, there is nothing more to prevent a ventilation of the spring-loaded cylinders, as long as there is a person in the driver's cab of the commercial vehicle; the latter is ensured by a check of the presence of the indicator.
In this respect, it is especially beneficial that the signal device used is a light which conventionally indicates the detention of the vehicle by means of the parking brake system, that the light flashes when the minimum pressure is overshot and the parking brake is locked, and that the light is extinguished when a pressure threshold in the spring-loaded cylinder is overshot. The normal sequence for starting a commercial vehicle equipped with the air treatment system according to the invention will, therefore, be that the driver switches on the ignition and thus induces a pressure build-up in the air treatment system. At this point in time, the parking brake system is still ventilated, so that the vehicle is detained. The lamp for the parking brake system lights up in the usual way. Pressure will subsequently build-up in the air treatment system, and a minimum pressure for operating the service brake system is overshot. At this point in time, the lamp begins to flash, so that the driver is advised that he can release the parking brake system. For this purpose, the driver opens the handbrake valve, if this has not already been done at an earlier point in time, and makes the electrically evaluatable indicator available, for example by tapping the brake pedal or by fastening a safety belt or by the fact that the safety belt is already fastened. As soon as a pressure threshold is overshot in the spring-loaded cylinders, the light is extinguished completely, thus indicating that the parking brakes are released.
The invention builds on the generic method in that an electrically actuable valve is provided, by which a supply of the compressed air outlet with compressed air can be prevented, in that, when a person for driving the commercial vehicle is present, an electrically evaluatable indicator may be made available, and in that the electrically actuable valve prevents the supply of the compressed air outlet with compressed air when the indicator is absent. In this way, the advantages and special features of the air treatment system according to the invention are also implemented within the framework of a method. This also applies to the especially preferred embodiments of the method according to the invention, which are given below.
There is beneficially provision for the compressed air outlet to be supplied with compressed air via an overflow valve and for the electrically actuable valve to be a solenoid valve which shuts off the overflow valve in at least one switching state.
The method according to the invention is particularly advantageously developed in that the solenoid valve is a 3/2-way valve which, in a first switching state, ventilates a control inlet of the overflow valve and, in a second switching state, acts with pressure upon the control inlet of the overflow valve, with the result that the overflow valve is shut off.
It is preferable that the second switching state of the 3/2-way solenoid valve is brought about by the application of current to the 3/2-way solenoid valve.
In one embodiment of the method according to the invention, there may be provision for the solenoid valve to be supplied centrally with compressed air.
It may also be beneficial, however, that the solenoid valve is supplied with compressed air by at least one service brake circuit.
In the method according to the invention, there is beneficially provision for the electrically evaluatable indicator to be made available as a result of the actuation of a pedal in the driver's cab of the commercial vehicle.
It is preferable that the electrically evaluatable indicator is made available as a result of the fastening of a safety belt in the driver's cab of the commercial vehicle.
It may likewise be expedient that the electrically evaluatable indicator is supplied directly or indirectly to an electrical control via a data bus, and that the electrically actuable valve is actuated by the electrical control.
The method according to the invention is advantageously developed in that a signal device is provided in the driver's cab of the commercial vehicle. The signal device indicates that a minimum pressure for operating the service brake system is overshot, and in that the compressed air outlet to be supplied with compressed air in the event of the overshooting of the minimum pressure and with the indicator present.
Furthermore, there is advantageously provision for the signal device used to be a light, which conventionally indicates the detention of the vehicle by means of the parking brake system, for the light to flash when the minimum pressure is overshot and the parking brake is locked, and for the light to be extinguished when a pressure threshold in the spring-loaded cylinder is overshot.
The invention relates, furthermore, to a commercial vehicle having an air treatment system according to the invention.
Advantageous embodiments of the invention are described and claimed herein.
The invention is based on the recognition that, as a result of the requirement for an electrically evaluatable indicator as a precondition for the ventilation of the spring-loaded cylinders of the parking brake system, additional security in the release of the parking brake system is made available. Thus, within the scope of the invention, there may be the requirement that a driver is present in the driver's cab of the commercial vehicle in order to permit the ventilation of the spring-loaded cylinders.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.